1,721,140 research outputs found
Mathematical modelling of blood perfusion and oxygen transport in the cerebral microvasculature of ischemic stroke
No full textMost frequently (80%) strokes result from the occlusion of one or several brain vessels and are called ischemic strokes (in other cases, strokes are hemorrhagic strokes). Measurements of hemodynamics and oxygen delivery on microscopic scales are technically difficult or impossible in many cases, especially during brain activity. One way to study the disease is to establish mathematical models to better understand the dynamic process of blood perfusion and oxygen transport in an ischemic stroke. In this paper, we propose a mathematical modeling system to investigate the haemodynamics and oxygen transport through a 2D cerebral microvascular network during ischemic stroke. The microvessel network is based on the anatomical brain microcirculation structure. The haemodynamic calculation is carried out on the microvessel network by fully coupling the intravascular blook perfusion, the trans vascular flow and the interstitial fluid flow. In addition, th compliance of microvessels and blood rheology with hematocritic distribution are also considered. The coupling procedure is based on the iteratively numerical simulation techniques in our previous study for tumour microvessels. The oxygen delivery is described by the time-varying oxygen advection diffusion equation which includes oxygen diffusion and advection in individual microvessel segments, oxygen diffusion and advection in individual microvessel segments, oxygen flux across the vascular wall, and then oxygen diffusion and consumption within the brain tissue. The hemodynamic information and oxygen distribution are investigated under physiological and pathological conditions
Higher order spectra based support vector machine for arrhythmia classification
No full textHeart rate variability (HRV) refers to the regulation of the sinoatrial node, the natural pacemaker of the heart by the sympathetic and parasympathetic branches of the autonomic nervous system. HRV analysis is an important tool to observe the heart’s ability to respond to normal regulatory impulses that affect its rhythm. Like many bio-signals, HRV signals are non-linear in nature. Higher order spectral analysis (HOS) is known to be a good tool for the analysis of non-linear systems and provides good noise immunity. A computer-based arrhythmia detection system of cardiac states is very useful in diagnostics and disease management. In this work, we studied the identification of the HRV signals using features derived from HOS. These features were fed to the support vector machine (SVM) for classification. Our proposed system can classify the normal and other four classes of arrhythmia with an average accuracy of more than 85%
PHYSIOLOGICALLY RELEVANT EXPRESSION & FUNCTIONAL CHARACTERIZATION OF PLASMODIUM(P.) FALCIPARUM DERIVED VARIANT STEVOR ANTIGENS USING BIOPHYSICAL ASSAYS
Full text linkPh.DDOCTOR OF PHILOSOPH
The Anisotropy of Bone Lamellae as a Function of Diverse Fibril Orientation Patterns
No full textIn this study, the homogenized anisotropic elastic properties of single bone lamellae are computed. The lamella itself is modeled by a finite element unit cell method and the underlying hierarchical levels of bone are described by a multiscale mean field model. The resulting stiffness tensor is utilized to calculate indentation modules for multiple indentation directions in the lamella plane which are then related to nanoindentation experimental results.
Diverse fibril orientation patterns are taken into account and are compared: The orthogonal plywood pattern, the twisted plywood pattern, a 5-sublayer pattern and an x-ray diffraction based pattern.
Results show, that in the osteon's axial direction, the model results of all investigated fibril orientation patterns are inside the standard deviation range of the experimental nanoindentation results. In circumferential direction, the twisted and orthogonal plywood patterns are too stiff compared to the experiments. These two patterns have equal stiffness properties in axial and circumferential direction which was not observed in the measurements. The 5-sublayer or the x-ray diffraction based pattern have a clear privileged stiffness alignment and match the experimental findings qualitatively.
This work shows that the variety of fibril orientation patterns leads to qualitative and quantitative differences in the lamella elastic mechanical behavior. The study is a step towards a deeper understanding of the structure - mechanical function relationship of bone lamellae
EFFECTS OF FLUID SHEAR STRESS ON MESENCHYMAL STEM CELL CONTRACTILITY AND FATE
Full text linkPh.DPH.D. IN MECHANOBIOLOGY (FOS
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